PHILADELPHIA (CBS) – We know that stress is bad for us – there is no doubt about that but, according to a report from the journal Human Reproduction, stress may lead to infertility.

There is a chemical in the saliva called salivary amylase, which can be used to measure stress, and researchers in Michigan and Texas studied nearly 400 couples as they tried to get pregnant for 12 months by following the levels of salivary amylase.

What they found is that higher levels of this salivary amylase were associated with a longer wait for pregnancy and an increased risk of infertility.

Those with high levels had double the risk of infertility. Those who argue against the study say there are factors that can increase the levels of salivary amylase other than stress: alcohol, caffeine and cigarettes included.